


Songs in the Key of Brettsey

by sugarspice623



Category: Chicago Fire
Genre: Best Friends, F/M, Friends to Lovers, Slow Burn
Language: English
Status: In-Progress
Published: 2021-01-14
Updated: 2021-03-01
Packaged: 2021-03-12 07:00:51
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,024
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28756275
Author URL: https://archiveofourown.org/users/sugarspice623/pseuds/sugarspice623
Summary: It's the same old song and dance being played between Sylvie Brett and Matt Casey. They know how they feel about each other, but will they act on it?
Relationships: Sylvie Brett/Matthew Casey
Comments: 23
Kudos: 58





	1. don't open old wounds

**Author's Note:**

> Hey everyone!! My name is Megan. This is my first work on AO3! I'm so excited to be writing this story for you all. I decided to put this on here because there's more Brettsey stories on here than on FF.net. Speaking of, I do have stories posted on there(my account name is the same as AO3), but since I can't import them to AO3 from FF, they're staying on there. 
> 
> This story will be a collection of moments between Brett and Casey. A little bit of slow burn in the first couple chapters, but I guarantee you that it will be pretty early on in the story when they get together. Each chapter will be the title or lyrics from a song, which I do not own. All rights to those songs go to their respective owners. 
> 
> Anyway, here is the first chapter for you all to enjoy! It is pretty short, but I think you guys will like it. It's based off of last night's episode(9x03) because I felt the Molly's scene should've had more than what we got, don't you think?

_I think I could love you til’ the day that you die_

_If you let me love you when the timing is right_

_And if they said they had to, I swear I’d wait my whole life_

_I think I could love you til’ the day that you die_

_-Old Wounds by PVRIS_

Sylvie and Stella were sitting at a two-person table at Molly’s talking about the infamous kiss that happened between Sylvie and Matthew Casey, the captain of Firehouse 51. Sylvie was telling Stella all about it, even the details. Stella even talked about her boyfriend, Lieutenant Kelly Severide’s weird behavior. Even Sylvie was puzzled by that. All the sudden, Casey walked in, small bandage on head from the accident earlier in the shift. He ordered a whiskey from Herrmann, then stared at Sylvie, who returned it. “You know what? Make it double.” Herrmann kept pouring the whiskey. Matt looked at Sylvie again. Once he got his whiskey, he walked over to the two women sitting at the table. “Hey, ladies,” Matt said. Stella and Sylvie greeted him back, but it wasn’t a happy greeting and understandably so. “Sylvie, can I talk to you outside for a minute?” Sylvie was confused, but she nodded. The two of them started to walk outside when Stella started talking. “Hey, have you seen or heard from Kelly at all after shift?” “Not that I know of. When we were talking during our cigar chat, he looked at you, but I haven’t heard anything else from him. Sorry.” Stella frowned, then she exchanged a smirk with Herrmann when Brett and Casey were walking out together.

* * *

Casey and Brett got outside in the freezing cold when Sylvie asked the question that was on her mind. “Matt, what is this about?” Matt took a breath before he responded. “Sylvie, when you asked me about Gabby the other night, I said what I said because it caught me completely off guard. I was enjoying the moment we had, which like I said before, I didn’t regret any of it whatsoever, and then you sprung that on me and I didn’t know what to say. To be honest, I haven’t even contacted or thought about Gabby these past few months. She asked me to go to Puerto Rico with her twice, and I’ve said no to her both times. I even got a voicemail from her after she left last year, but I didn’t respond back to it. I’m a Chicago guy, Sylvie. You’re the only person that has been on my mind all this time. I can’t stop thinking about you. But, if you want space, I will respect that wish and give it to you.” Sylvie looked at him with such awe. She has been waiting to hear this for a long time. “I do want space, but I’m very happy with everything you’ve told me. I hope you can understand that.” Matt nodded.

“I can.” Sylvie started to walk away, but stopped and turned around when she heard Matt call her name. “I know you haven’t had the best luck with relationships, but you should know that I’m going to fight for you. For us. I want to be the guy that’s in your life forever and I want you in my life.” Sylvie walked over and hugged him. Matt was shocked. He accepted the hug, knowing that this was all he was going to get for now and he was content about it. Sylvie heard what he had to say, and they made progress in their relationship. What could get any better than this. 

Little did they know, Stella was watching out the window with another smirk glued onto her face. At least she got some happiness today.


	2. you were in my t-shirt

**Summary for the Chapter:**

> Sylvie's been wearing Matt's t-shirts. When he has none left, he gets more. The cycle repeats.

**Notes for the Chapter:**

> Hey everyone! I had a new chapter up for this story earlier today, but I deleted it because I realized that I didn't like it after all and it didn't make sense with what the story is supposed to be about. So, I'm making it up to you by posting a brand new chapter for you all. This one is corny and lighthearted and there will be a bit of a time jump, so stay tuned! Hope you enjoy!

" _Oh no, baby no, I can't lie_

_Cause you sure look good in my t-shirt_

_Oh no, baby no, I can't lie_

_You look good on my mind"_

_-T-Shirt by Thomas Rhett_

Well, happiness is all around Firehouse 51 again, just like it should be. Brett and Casey finally got their act together a couple weeks after the Grainger/Sydney mess and started a relationship. They couldn't be happier. Stella was happy as well because when her best friend is happy, she's happy. Plus, she's been waiting almost 2 years for them to get together, so she gets instant bragging rights.

Sylvie was currently in her apartment deciding what to wear to the firehouse before she replaces the outfit with her work uniform. She doesn't know why she's taking a hard time to decide, it's not like she's going to the CFD gala or anything. Although, she would knock Matt dead there too if that were the case. She picked out a pair of jeans, one of her signature jackets, and pulled open her shirt drawer where lots of new t-shirts resided. She didn't mean to grab them after she left Casey's apartment, but they were so soft and comfy that she couldn't let them go when she got back to her place. A gray one ended up in her hand. _I can't wait to see Matt's reaction!_ she thought. 

* * *

Meanwhile, Casey was in his room trying to find a t-shirt to wear after shift. Yes, he actually got up on time today. Ever since he started dating Sylvie, he's been waking up normally again and not oversleeping like a miserable lovesick puppy. He looked in his closet, but none were in there. He then opened his t-shirt drawer and none were in there either. _Unbelievable!_ he thought. Matt had one idea as to where his t-shirts went, and the minute he thought of it, he smirked. _That little sneak!_ He trekked on over to Kelly's room unnoticed until he rapt on the door. 

"Yeah, Case?" Kelly said. He was too busy packing his bag for after shift, so his back was turned to Casey at the moment. 

"Can I borrow one of your t-shirts?" Casey asked. Kelly turned around and looked at him dumbfounded. 

"Did I just hear you correctly?" 

"Yeah. Sylvie took all of mine and I can't leave the firehouse shirtless after shift, so I need a t-shirt!" 

"Oh, so you're in that stage of the relationship now? I see how it is!" Kelly teased him as he went to get a shirt. 

"Shut up!" Casey caught the shirt that Kelly threw at him. "Thanks man." 

"Yep." Kelly just chuckled and shook his head. _Only those two,_ he thought. 

* * *

Shift ended and Matt was going to the locker room to change out of his work clothes. He ran into his lovely girlfriend on the way there.

"Hey, babe," Sylvie said. 

"Hey. Is that my shirt you're wearing?" Matt replied, looking up and down at her. 

"Yep. You like?" 

"As a matter of fact, I do. You look better in them than I do. It's hot. Although, I can't help but wonder where all the rest of them went. I went looking for one this morning and I had to borrow a shirt from Kelly since there were no shirts to be found in my drawer. Who was the culprit?" 

"Alright. You caught me! I'm sorry." 

"Well, at least it's you and not somebody that robbed the place overnight." 

"I'm glad you're not mad at me about it." The two of them shared a laugh."I'll see you later?" 

"You know it. Later babe." He kissed her and she walked off to her car. He looked back at her as she was walking away. _God, she's hot!_ Matt thought. He couldn't wait for tonight when they would see each other again. 

* * *

Matt and Sylvie planned a night in at his apartment since it was supposed to snow overnight and they didn't want to risk going to Molly's in that kind of weather. He was sitting on the couch waiting. Luckily, he didn't have to wait long as he heard a knock at the door.

"Hey, Syl," Matt said, smiling at her the minute he opened the door. "What's in that bag you got there?" 

"Hey. Oh, you know, a little present for you. It's the least I could do after I stole things of yours." 

"Well, let's find out what it is, shall we?" The happy couple made their way over to the couch so Matt could open his gift from Sylvie. When he pulled new t-shirts out of the bag, he feigned shock. "New shirts. I've been needing some of them!" 

"I know you so well, don't I? Although, a couple of them might be gone over the next couple of days." 

"Oh, so these are for your benefit? I see." 

"You catch on rather quick, Matt Casey." 

"That I do, Sylvie Brett." Matt put the shirts back in the bag on the floor and pulled out the remote. He put on a movie he found on Hulu that he hoped Sylvie would like. She put her head on his shoulder and he leaned back, allowing her to get comfy. Eventually, she fell asleep during the movie. All he could do was tuck a blanket around both of them because he knew he would be down for the count in a little bit as well. He put his arm around her and tried to fall asleep. 

* * *

Over the next few days, Sylvie proved her point. Matt's t-shirts were gone again and the cycle repeated. Stella and Kelly were laughing when Matt couldn't find another shirt again. Well, Kelly moreso than Stella. Stella applauded Sylvie for doing this. When they got to the firehouse, Sylvie finally gave him some of his shirts back. He couldn't be happier about that since he's been lightly scolded by Kelly already for having to borrow his t-shirts for an entire week. Matt loved that he can be a dork around Sylvie because she's just as dorky and corny as he is, and he loves her for it. With Sylvie, he can be the true Matt Casey, who he really is: happy, carefree, fun loving, dorky, future father, and maybe later on down the line, husband. He can't wait for that day to come. 


	3. my right to be hellish

**Summary for the Chapter:**

> When Herrmann goes on vacation with his family, his replacement is somebody that no one expects. Casey is livid when he sees who it is.

**Notes for the Chapter:**

> Hey everyone!! A new one shot is comin' your way today. This one is my take on how 9x08 could play out. It's also kind of a prequel of sorts to the last chapter. When I found out that Grainger would be coming to 51, I knew that it would be good, so I had to write about it because jealous Matt truly is a thing of beauty. Plus, I'm basing it off of one of my all time favorite songs! Hope you enjoy!! 
> 
> Side note: To all my fellow One Tree Hill fans, is it just me or does the Brettsey situation right now kinda remind you of the whole Brucas "non-exclusive" thing they had going? Obviously, there are differences between those two situations, but it's bringing me back a bit. Let me know! I would love to hear your thoughts on this!

_  
_ " _I turn my chin music up_

_And I'm puffing my chest_

_I'm getting red in the face_

_You can call me obsessed"_

_-Jealous by Nick Jonas_

Everyone at Firehouse 51 was ready for their shift to start. Herrmann, however, wasn't there because he took furlough to go on vacation with his family. There will be a replacement for Engine in the meantime, but as to who it is, nobody knows. That's what the meeting in the briefing room is for. All of the firefighters were either sitting or standing in the room waiting in anticipation for Boden's announcement. The man himself walked in with an emotionless look on his face. 

"As you all know, Herrmann is out on furlough with his family, so there will be somebody taking over Engine in his place," Boden said. 

"Do you know who it is, Chief?" Stella asked. 

"Yes, I do." Boden then gave a signal and in walked somebody that nobody expected. Sylvie, however, was happy as a clam when she saw him. 

"Greg!" She ran up and hugged him. All eyes were on Casey, except for Kelly and Stella. They looked at each other, both thinking the same thing. _Oh, this oughta be good._ Casey clenched his fists in response to what he is seeing right in front of him. This was definitely going to be a good day for entertainment and everyone was more than happy to sit back, relax, and enjoy the show. 

* * *

Engine and Ambo were out on a call, which meant that Casey was in his quarters because he didn't want to deal with anyone right now. A few minutes later, they returned and no more than they did, Casey was back in the common room. He regretted it, however, because he was disgusted at seeing Sylvie and Greg being all lovey-dovey with each other. He then walked up to the two of them. 

"Grainger. " Greg looked at him. "You may be here temporarily, but I am the captain, and whatever I say goes. You can lead your team, but in terms of the overall call, I call the shots around here." 

"I know," Grainger replied. 

"Good. Just wanted to make that clear." Sylvie looked between the two of them in confusion, then at Stella, who looked just as confused. _What is his problem?_ Sylvie thought. She decided to go after him to find out. 

"Matt!" He turned around when he saw her. "What was that out there? Greg is not going to be here that long--" 

"Yeah, whatever." Matt walked away. Sylvie was appalled at how he was acting. This was not the Matt Casey that she knows and still loves. 

* * *

Matt walked back to his quarters and grabbed two cigars. Then, he walked towards Kelly's quarters holding up the cigars with an angry look plastered on his face. Kelly sighed, grabbed his beanie and jacket, then followed him out. 

"Of all the weeks Herrmann took furlough, this had to be the one? Of course," Matt said. 

"That may not have been by choice. Boden probably told him to take it before he lost it," Kelly replied, trying to see a confounding factor in his friend's statement. 

"Still, my luck is the worst." 

"Well, this wouldn't have happened if you weren't such a dumbass." Casey glared at his best friend. "Hey. I'm gonna tell you what a wise man once told me: that feeling, that connection, it won't go away just 'cause you don't want it to be there." 

Matt then chuckled at his own best friend's words, or his words being used against him. "Well played, Sev, well played." It was Kelly's turn to chuckle. The two of them continued to smoke cigars and talk for another half hour before going back inside the firehouse. Casey needed that talk with Severide and although he wouldn't admit it to anyone, he needed Kelly shooting his own words that he said to him not that long ago back in his face. 

* * *

Nightfall arrived, even though shift ended hours ago. Casey was sitting around on the couch in the apartment watching the Blackhawks game. He had a beer in his hand and was perfectly content with what he was doing. That is until he heard a knock at the door. 

"Sylvie," Matt said when he saw who was on the other side. 

"Hi Casey," Sylvie replied. It stung hearing his last name come out of her mouth, but truth be told, he probably deserved it. He moved out of the way to let her walk inside. "Are Stella and Severide around?" 

"No. They went out. You need something?" 

"Yes, actually I do. I need to know why you were such an ass to Greg on shift today." That came out harsher than Sylvie intended, but it needed to be asked. 

"I-I wasn't trying to be--" 

"Yes you were, Matt, and you know it." Matt turned around, not wanting to deal with this. "Why were you an ass?" Sylvie repeated the question. 

Matt then turned around. "BECAUSE I LOVE YOU, OK?" Sylvie was shocked. "It killed me seeing you with Grainger today. It killed me seeing you with Grainger all those other times too." 

"Then why did you sleep with Sydney?" 

"Because I thought that it would make my feelings for you go away, but they didn't. I know I hurt you by doing that, and it killed you seeing me with her, but you were with Grainger, and you seemed happy, so I let you be." 

"You could've told me that." 

"I know and I'm an idiot. I deserved everything I've gotten these past few weeks because I'm too stubborn to say how I really feel to anyone besides Sev. Plus, you wanted space and I wanted to respect that." 

"Ok. Well, if you really love me, then why did you say that you didn't know if you would go with Gabby if she came back?" 

"Again, I'm a damn idiot. Sylvie, a part of me will always love and care about Gabby. I'm just not in love with her anymore. You've been the only thing on my mind this past year and a half and I haven't even thought about Gabby in that time, so I'm going to say it again: my feelings for you are real. They've been real for a long time. I'm a Chicago guy. I'm not going anywhere." 

"Why didn't you say that the first time?" 

"Because you caught me off guard. I was so in the moment that it was taking me a minute to process your question. I can list all of the reasons why I love you off the top of my head and if you need to hear every single one of them, then I will gladly tell you."

"No need. I think you made your point pretty clear." Sylvie took her coat off, put her purse down, walked to him, and kissed him. Matt was so happy inside right now. When Sylvie pulled away, Matt kissed her back. They made their way to the bedroom where they ended up for the rest of the night. 

* * *

Kelly and Stella walked into the apartment after their night out at Molly's, unaware of what was going on in the other bedroom. Kelly looked around wondering where Matt was since he was on the couch when they left. 

"Casey? Case? Matt?" Kelly kept calling out his name, but there was no response. He then walked over to Stella, who was grinning at the sight in front of her. She turned around.

"That's Brett's stuff on the table." "So?" Kelly asked. "You know what this means, right?" Kelly was confused. "I WON THE BET!!" Stella pumped her fists in the air and started dancing around, proud of the bragging rights she gets to unleash on the rest of the firehouse when she sees them next. Kelly couldn't help but laugh at his silly girlfriend he loved. Both of their best friends were finally happy and they wouldn't have it any other way.


End file.
